The major aim is the characterization of prostaglandin (PG) synthetase, the initial enzyme of PG synthesis, under conditions which approximate those found in a cell. Normal hemostasis is affected by PG synthesis in blood elements. A balance appears to exist between the clot-promoting effect of platelet thromboxane A2(TxA2) and the anti-thrombotic effect of endothelial prostacyclin (PGI2). The TxA2-PGI2 balance may be altered in vascular disease, prompting thrombotic complications such as myocardial infarction and stroke. Anti-thrombotic drugs such as aspirin and sulfinpyrazone affect PG synthetase and may alter the TxA2-PGI2 balance to benefit the patient with vascular disease. However, we are unsure of how to use these drugs most effectively. Some of the uncertainty stems from a lack of knowledge about PG synthetase itself; namely, its heme-binding characteristics, its liposome binding properties and the nature of its reductant. These aspects of the enzyme from vesicular gland will be studied in detail in order to provide a better understanding of how this enzyme works in a cell and how anti-thrombotic drugs influence the enzyme. A second aim is the study of human platelet PG synthetase by means of an antiserum directed against the enzyme. Specifically, subcellular localization studies of the platelet enzyme will be performed, proteins associated with the enzyme in platelets will be defined, and the amount of platelet enzyme in patients with abnormal platelet function will be measured by a radio-immune assay. The long-term objective of the work is a detailed characterization of prostaglandin synthesis and a clear definition of how anti-thrombotic agents affect synthesis. The project relates most clearly to the field of hemostasis; specifically, the role of PG synthesis in hemostasis and the use of anti-thrombotic drugs.